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Comparison between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas
Clinical Radiology (2006) 61, 800e802
CORRESPONDENCE
Comparison between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas SirdWe read with great interest the article by Xu et al.1 reporting that tumour response to thermal ablation, such as radiofrequency ablation (RFA) and percutaneous microwave coagulation therapy (PMCT), was the most predictive factor for longterm survival in patients with hepatocellular carcinomas (HCCs). However, using univariate analysis, prognostic factors of their overall survival and disease-free survival for patients with HCCs showed no significant differences between RFA and PMCT. This was probably because they enrolled many patients [58(42.3%) of the 137 patients] with large tumours, measuring more than 3 cm in diameter, that would probably have been difficult to eradicate by percutaneous procedures.2 There have only been a few studies3,4 comparing the clinical response between RFA and PMCT. They also reported that the therapeutic effect on patients with various sized tumours showed no significant differences between the two medical treatments. We evaluated the therapeutic effect and safety of these two procedures for the treatment of small HCCs measuring less than 3 cm in maximum diameter. The following data have not been published and are not in press. Fifty-eight patients with 64 nodules who were treated with RFA using a cool-tip electrode (Radionics, Burlington, MA, USA) during the period from August 2001 to January 2006 were compared with 72 patients (84 nodules) who underwent PMCT (Azwell Inc., Osaka, Japan) from June 1997 to March 2005. Regarding background factors, there was no significant difference in the mean age (68 versus 66), male:female ratio (41:17 versus 56:16), viral markers (B/C/NBNC: 4/49/5 versus 5/61/6), Child-Pugh classification (A/B/C: 41/12/5 versus 57/13/2), or tumour stage (I/II/III/ IV: 30/23/5/0 versus 29/28/14/1). As for the tumour nodules, there was no significant difference in tumour size (mean, range: 1.8, 0.7e2.8 cm versus 1.9, 0.8e2.9 cm) or tumour histology (well/ moderately/poorly: 33/26/5 versus 46/32/6). RFA or PMCT were repeated until complete tumour necrosis with a surrounding safety margin was confirmed by contrast computed tomography
(CT). Informed consent was obtained from each patient before treatment. The therapeutic and adverse effects were compared between the two procedures. The average numbers of treatment sessions for RFA and PMCT was 2.2 0.6 and 3.4 1.0, respectively, being significantly lower in the RFA group (P < 0.001). The maximal/minimal diameters of the necrotic area following RFA and PMCT were 2.9/2.6 cm and 2.6/1.9 cm, showing that RFA created a significantly larger area of necrosis (p < 0.001). The local recurrence rate after RFA was significantly lower (Fig. 1) and the survival rate after RFA was significantly higher compared with the PMCT group (Fig. 2). The low rate of local tumour recurrence after RFA may have contributed to the better prognosis of the RFA group. With regard to adverse effects, the incidence of minor complications, such as pain, fever, bile duct injury, pleural effusion and ascites were significantly more common in PMCT patients. Serious adverse reactions, such as liver abscess, intraperitoneal haemorrhage, and biliary peritonitis, only occurred in the PMCT group. The incidence of major complications has been reported to be higher after PMCT compared with RFA.5,6 Therefore, the better prognosis of the RFA group may be related to the significantly higher incidence of adverse reactions and the occurrences of serious adverse reactions after PMCT.
Figure 1 The local recurrence rate was significantly lower in the RFA group than in the PMCT group.
Correspondence
801
Comparison between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas d a reply
Figure 2 The overall survival rate of the RFA group was significantly higher than that of the PMCT group.
In conclusion, the present study suggested that RFA is a more useful method for the treatment of small HCCs compared with PMCT because it is minimally invasive and achieves a low local recurrence rate, a high survival rate, and extensive necrosis after only a few treatment sessions.
References 1. Xu H-X, Lu M-D, Xie X-Y, et al. Prognostic factors for long-term outcome after percutaneous thermal ablation for hepatocellular carcinoma: a survival analysis of 137 consecutive patients. Clin Radiol 2005;60:1018e25. 2. Beaugrand M, N’kontchou G, Seror O, et al. Local/regional and systemic treatments of hepatocellular carcinoma. Semin Liver Dis 2005;25:201e11. 3. Shibata T, Iimura Y, Yamamoto Y, et al. Small hepatocellular carcinoma: comparison of radio-frequency ablation and percutaneous microwave coagulation therapy. Radiology 2002; 223:331e7. 4. Lu M-D, Xu H-X, Xie X-Y, et al. Percuteneous microwave and radiofrequency ablation for hepatocellular carcinoma: a retrospective comparative study. J Gastroenterol 2005; 40:1054e60. 5. Shimada S, Hirota M, Beppu T, et al. Complications and management of microwave coagulation therapy for primary and metastatic liver tumors. Surg Today 1998;28:1130e7. 6. de Baere T, Risse O, Kuoch V, et al. Adverse events during radiofrequency treatment of 582 hepatic tumors. AJR Am J Roentgenol 2003;181:695e700.
K. Ohmoto, S. Yamamoto Kawasaki Medical School, Kurashiki, Japan E-mail address: [email protected] ª 2006 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2006.04.015
Sir d Radiofrequency (RF) ablation and microwave ablation are two common thermal ablation techniques for treatment of hepatocellular carcinoma (HCC).1e4 Comparison between them in terms of local therapeutic efficacy, complication and longterm outcome is valuable, which may provide useful information with respect to treatment method selection in different clinical settings. There have been two studies that intentionally compared RF and microwave ablation in treating HCC. In a randomized controlled trial by Shibata et al.1 complete ablation, major complication, and local recurrence did not approach statistical significance. However, the number of treatment sessions per nodule and the mean time for a treatment session was significantly different between the two techniques. Similar results were obtained in another retrospective study by Lu et al.3 The results of the two series are not surprising. Although the mechanisms of energy output for the two methods are different, both RF and microwave ablation result in cytotoxic temperatures and then induce coagulation necrosis of the tumour.4 If different clinical results between them were obtained, the possible factors may be the differences in individual devices, treatment strategies, manipulation skill or experience, when taking no account of tumour or patient clinical characteristics. As the study of Ohmoto et al.5 has shown, it is true that single ablation using RF creates a larger coagulation volume than does microwave ablation, however, using special ablation techniques such as overlapping ablation or multiple insertion of electrodes, equivalent coagulation volume is achievable. Ohmoto et al.5 also mentioned that the high incidence of complications after microwave ablation was related to inferior prognosis, but they did not statistically analyse the difference between two groups. The risks with both RF and microwave ablation are largely same, which include those related to applicator placement, those of unwanted thermal damage and hepatic decompensation, thus the differences between them needs further investigation. The study of Ohmoto et al.5 and our study only revealed the results of a special scenario with special devices. Further refinement of the techniques of RF or microwave ablation may lead to different results. Using a reformative Teflon-coated microwave electrode and a cooled-tip RF single electrode, Shibata et al.6 found that microwave ablation achieved superior coagulation volume compared with RF
CORRESPONDENCE
Comparison between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas SirdWe read with great interest the article by Xu et al.1 reporting that tumour response to thermal ablation, such as radiofrequency ablation (RFA) and percutaneous microwave coagulation therapy (PMCT), was the most predictive factor for longterm survival in patients with hepatocellular carcinomas (HCCs). However, using univariate analysis, prognostic factors of their overall survival and disease-free survival for patients with HCCs showed no significant differences between RFA and PMCT. This was probably because they enrolled many patients [58(42.3%) of the 137 patients] with large tumours, measuring more than 3 cm in diameter, that would probably have been difficult to eradicate by percutaneous procedures.2 There have only been a few studies3,4 comparing the clinical response between RFA and PMCT. They also reported that the therapeutic effect on patients with various sized tumours showed no significant differences between the two medical treatments. We evaluated the therapeutic effect and safety of these two procedures for the treatment of small HCCs measuring less than 3 cm in maximum diameter. The following data have not been published and are not in press. Fifty-eight patients with 64 nodules who were treated with RFA using a cool-tip electrode (Radionics, Burlington, MA, USA) during the period from August 2001 to January 2006 were compared with 72 patients (84 nodules) who underwent PMCT (Azwell Inc., Osaka, Japan) from June 1997 to March 2005. Regarding background factors, there was no significant difference in the mean age (68 versus 66), male:female ratio (41:17 versus 56:16), viral markers (B/C/NBNC: 4/49/5 versus 5/61/6), Child-Pugh classification (A/B/C: 41/12/5 versus 57/13/2), or tumour stage (I/II/III/ IV: 30/23/5/0 versus 29/28/14/1). As for the tumour nodules, there was no significant difference in tumour size (mean, range: 1.8, 0.7e2.8 cm versus 1.9, 0.8e2.9 cm) or tumour histology (well/ moderately/poorly: 33/26/5 versus 46/32/6). RFA or PMCT were repeated until complete tumour necrosis with a surrounding safety margin was confirmed by contrast computed tomography
(CT). Informed consent was obtained from each patient before treatment. The therapeutic and adverse effects were compared between the two procedures. The average numbers of treatment sessions for RFA and PMCT was 2.2 0.6 and 3.4 1.0, respectively, being significantly lower in the RFA group (P < 0.001). The maximal/minimal diameters of the necrotic area following RFA and PMCT were 2.9/2.6 cm and 2.6/1.9 cm, showing that RFA created a significantly larger area of necrosis (p < 0.001). The local recurrence rate after RFA was significantly lower (Fig. 1) and the survival rate after RFA was significantly higher compared with the PMCT group (Fig. 2). The low rate of local tumour recurrence after RFA may have contributed to the better prognosis of the RFA group. With regard to adverse effects, the incidence of minor complications, such as pain, fever, bile duct injury, pleural effusion and ascites were significantly more common in PMCT patients. Serious adverse reactions, such as liver abscess, intraperitoneal haemorrhage, and biliary peritonitis, only occurred in the PMCT group. The incidence of major complications has been reported to be higher after PMCT compared with RFA.5,6 Therefore, the better prognosis of the RFA group may be related to the significantly higher incidence of adverse reactions and the occurrences of serious adverse reactions after PMCT.
Figure 1 The local recurrence rate was significantly lower in the RFA group than in the PMCT group.
Correspondence
801
Comparison between radiofrequency ablation and percutaneous microwave coagulation therapy for small hepatocellular carcinomas d a reply
Figure 2 The overall survival rate of the RFA group was significantly higher than that of the PMCT group.
In conclusion, the present study suggested that RFA is a more useful method for the treatment of small HCCs compared with PMCT because it is minimally invasive and achieves a low local recurrence rate, a high survival rate, and extensive necrosis after only a few treatment sessions.
References 1. Xu H-X, Lu M-D, Xie X-Y, et al. Prognostic factors for long-term outcome after percutaneous thermal ablation for hepatocellular carcinoma: a survival analysis of 137 consecutive patients. Clin Radiol 2005;60:1018e25. 2. Beaugrand M, N’kontchou G, Seror O, et al. Local/regional and systemic treatments of hepatocellular carcinoma. Semin Liver Dis 2005;25:201e11. 3. Shibata T, Iimura Y, Yamamoto Y, et al. Small hepatocellular carcinoma: comparison of radio-frequency ablation and percutaneous microwave coagulation therapy. Radiology 2002; 223:331e7. 4. Lu M-D, Xu H-X, Xie X-Y, et al. Percuteneous microwave and radiofrequency ablation for hepatocellular carcinoma: a retrospective comparative study. J Gastroenterol 2005; 40:1054e60. 5. Shimada S, Hirota M, Beppu T, et al. Complications and management of microwave coagulation therapy for primary and metastatic liver tumors. Surg Today 1998;28:1130e7. 6. de Baere T, Risse O, Kuoch V, et al. Adverse events during radiofrequency treatment of 582 hepatic tumors. AJR Am J Roentgenol 2003;181:695e700.
K. Ohmoto, S. Yamamoto Kawasaki Medical School, Kurashiki, Japan E-mail address: [email protected] ª 2006 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2006.04.015
Sir d Radiofrequency (RF) ablation and microwave ablation are two common thermal ablation techniques for treatment of hepatocellular carcinoma (HCC).1e4 Comparison between them in terms of local therapeutic efficacy, complication and longterm outcome is valuable, which may provide useful information with respect to treatment method selection in different clinical settings. There have been two studies that intentionally compared RF and microwave ablation in treating HCC. In a randomized controlled trial by Shibata et al.1 complete ablation, major complication, and local recurrence did not approach statistical significance. However, the number of treatment sessions per nodule and the mean time for a treatment session was significantly different between the two techniques. Similar results were obtained in another retrospective study by Lu et al.3 The results of the two series are not surprising. Although the mechanisms of energy output for the two methods are different, both RF and microwave ablation result in cytotoxic temperatures and then induce coagulation necrosis of the tumour.4 If different clinical results between them were obtained, the possible factors may be the differences in individual devices, treatment strategies, manipulation skill or experience, when taking no account of tumour or patient clinical characteristics. As the study of Ohmoto et al.5 has shown, it is true that single ablation using RF creates a larger coagulation volume than does microwave ablation, however, using special ablation techniques such as overlapping ablation or multiple insertion of electrodes, equivalent coagulation volume is achievable. Ohmoto et al.5 also mentioned that the high incidence of complications after microwave ablation was related to inferior prognosis, but they did not statistically analyse the difference between two groups. The risks with both RF and microwave ablation are largely same, which include those related to applicator placement, those of unwanted thermal damage and hepatic decompensation, thus the differences between them needs further investigation. The study of Ohmoto et al.5 and our study only revealed the results of a special scenario with special devices. Further refinement of the techniques of RF or microwave ablation may lead to different results. Using a reformative Teflon-coated microwave electrode and a cooled-tip RF single electrode, Shibata et al.6 found that microwave ablation achieved superior coagulation volume compared with RF